IDS2935 Module 9 Surveillance and Management of Arthropod-Borne Diseases

What is the definition of surveillance?

The act of watching over something.

What is the definition of survey?

A general study or inspection.

Until the early 20th century, vector-borne diseases were responsible for more _ deaths than all other causes combined.

Human

What are some facts about surveillance?

• Crucial to conduct routine surveillance

• Provides the basis for predicting disease
  outbreaks

• Permits timely intervention

_ _ and choice of sampling tools vary.

Surveillance methods

Passive or Active?
Which one (passive or active) does the Purpose, Pros and Cons list apply to?

Purpose:

• To access trends

• To identify risk factors for
  prevention and control

Pros:

• Inexpensive

• Can cover large areas

Cons:

• Under reporting

• Incomplete data

Passive

Passive or Active?
Which one (passive or active) does the Purpose, Pros and Cons list apply to?

Purpose:

• To validate passive surveillance
  systems

• To loosely track new invasions

Pros:

• More accurate and complete data

• Can produce early and timely data

Cons:

• Can be resource intensive

• Methodology must be well-developed

Active

What is the Estimation of Vector Density technique?

Based on the concept that high vector densities are associated with outbreaks of vector-borne diseases. Correlation between disease cases in human or animal hosts and estimates of vector density may be difficult to demonstrate and varies based on several factors.

What do sampling tools depend on?

The vector (or life stage of the vector) sought and the specific objectives of the surveillance operation.

What are light traps used for?

Useful for flying insects such as mosquitoes, sand flies, horse flies, etc. There are many variations

What are dippers used for?

Sampling mosquito larvae and pupae

What are sticky traps used for?

Glue-based traps used in pest control to catch and monitor insects

• They do not contain pesticides

• Traps cockroaches, spiders, beetles, mites, and other crawling insects

What is an ovitrap used for?

A mosquito trap where mosquitoes lay their eggs

• Eggs hatch and develop into pupae

• Once the adult mosquitoes emerge, they are trapped beneath the mesh

• Can act as an early warning signal to prevent mosquito-borne disease outbreaks

How to conduct Tick surveillance passively?

By examining ticks brought into health units or human cases, reporting the location of their most likely exposure to human health

How to conduct Tick surveillance actively?

When public health professionals collect ticks from their natural habitat

What is tick drag sampling?

An active surveillance method that involves dragging a large square of cloth (white or pale in color) over the ground to catch questing ticks

What does tick walk involve?

Wearing white clothing and walking along a standardized path, all ticks on the clothing are removed and identified

When tick walking/dragging, what colors are necessary so that ticks that stick to the cloth can be easily seen?

White or pale colors

Why is detection and identification of pathogens from arthropods and hosts important?

It is most useful for zoonotic diseases in which pathogens may be detected in vectors before the appearance of human or animal disease cases.

To detect pathogens, what needs to be dissected and examined for pathogens?

The internal organs of individual arthropods

What methods are used for detection and identification of pathogens from arthropods and hosts, and what can they routinely detect from each?

Microscopic examination

• Chagas disease

• Tick-borne parasites

Immunoassays

• Utilize antigens or antibodies conjugated to an enzyme for the detection of a positive reaction

What does source reduction do?

• Removal or permanent destruction of breeding sites

• For aquatic environments, the larval habitats may be destroyed by filling depression that collect water, by draining swamps, or by ditching marshy areas to remove standing water

• For terrestrial envionments, burning and vegetation management are useful

What is larviciding?

The regular application of chemical or microbial insecticides to water bodies to kill the aquatic immature forms of vectors

What are the two different classes of insecticides outlined by the lecture?

• DDT

• Pyrethroids

What are some examples of insecticides for larviciding?

Plant-derived insecticides are derived from plants

• Pyrethrins from Chrysanthemum flowers and azadirachtin from the neem tree

Other environmentally less disruptive methods

• Oils, microbial toxins, and insect growth regulators

What are some facts about insecticides for larviciding?

• Oils may be applied to the water surface to suffocate the larvae and pupae. Most oils in use today are rapidly biodegradable

• Examples are petroleum such as kerosene, diesel oil, and light distillate domestic fuel oils

One of the most common microbial toxins used for larvicing include toxins from the bacterium, Bacillus thuringiensis, which is also known as Bt.

What does Bt do?

Makes toxins that target insect larvae when eaten. In their gut, the toxins are activated. The activated toxin breaks down their gut, and the insects die of infection and starvation. Death can occur within a few hours or weeks

Toxins from the bacterium Bacillus thuringiensis var. israelensis (Bti) can be applied like..?

Chemical insecticides. They are very specific, affecting only mosquitoes, black flies and midges.

What are some characteristics of what Insect growth regulators (IGRs) can do?

• Compounds that retard or inhibit the growth of an insect, ultimately causing death

• Mimic juvenile hormones in young insects.

• Can be applied in the same way as a chemical insecticide

What are some personal protection measures?

Window screens, insecticide-treated nets, repellents (such as DEET), and wearing light-colored clothes, long pants, and long-sleeved shirts

What is biological control?

The use of living organisms to suppress pest populations.

• Mosquito fish (including Gambusia affinis) have largely been ineffective

What does sterile insect technique involve?

• Mass production and release of insects sterilized by gamma irradiation

• Sterilized males mate with wild females, but no offspring are produced

• Used to control Aedes aegypti mosquitoes in the United States

The use of drugs in arthropod-borne diseases takes two forms, what are these forms and what do they do?

• Chemoprophylaxis - use of drugs to prevent disease

• Chemotherapy - use of drugs to treat disease

What is the purpose of vaccines?

• Parasitic organisms possess proteins (antigens) on their external surfaces and elsewhere that may evoke immune responses in the host that allow the host to avoid disease or help to shorten the course and severity of the disease.

• Antigens that evoke responses from the immune system are immunogens and are said to be immunogenic